In a cloud storage system, a user may be limited by the network environment or the particular application features. Consequently, the user may need to perform multiple write operations to complete the writing of one data file. For example, when writing a large data file, a user usually needs to use append write mode. In a distributed cloud storage system, problems such as concurrent writes of a user and issues regarding data integrity need to be addressed, in order to support append write mode. Therefore, there is a need for techniques on how to support append write mode for a data file in a cloud storage system.